Scientists recreate the conditions that sparked complex life

The original version to This story Featured in Quanta Magazine.

Far from being single operators, most of them are unicellular Microbes In complex relationships. In the ocean, the soil, and your gut, they may fight, eat each other, and swap DNAOr they compete for nutrients, or feed on each other’s byproducts. Sometimes they become more intimate: one cell He may slip inside another person and make himself comfortable. If conditions are right, it may survive and be welcomed, leading to a relationship that may last for generations or billions of years. This phenomenon of one cell living inside another, called endosymbiosis, fueled the evolution of complex life.

Examples of endosymbiosis are everywhere. Mitochondria, the energy factories in your cells, They were once free-living bacteria. Photosynthetic plants owe the sugars produced by the sun to the chloroplast, which was also originally an independent organism. Many insects obtain essential nutrients Of the bacteria that live inside it. And researchers last year Discover “Nitroplast” It is an endosymbiont that helps some algae process nitrogen.

Much of life depends on internal symbiotic relationships, but scientists struggle to understand how they happen. How does the inner cell evade digestion? How does it learn to reproduce within its host? What makes the random merging of two independent beings into a stable and lasting partnership?

Now, for the first time, researchers have seen the opening choreography of this microscopic dance Induction of endosymbiosis in vitro. After injecting bacteria into the fungi—a process that requires creative problem-solving (and a bicycle pump)—the researchers were able to elicit cooperation without killing the bacteria or the host. Their observations offer a glimpse into the conditions that make it possible for the same thing to happen in microbial life.

The cells even adapted to each other faster than expected. “To me, this means that organisms want to live together, and that coexistence is the norm,” he said. Vassilis Kokourisa mycologist who studies the cell biology of symbioses at VU University in Amsterdam and was not involved in the new study. “So this is very big news for me and this world.”

Early failed attempts reveal that most cellular love relationships are unsuccessful. But by understanding how, why and when organisms accept endosymbionts, researchers can better understand key moments in evolution, and perhaps develop artificial cells engineered with super-powerful endosymbionts.

Cell wall penetration

Julia Forholta microbiologist at the Swiss Federal Institute of Technology in Zurich, Switzerland, has long puzzled over the conditions for endosymbionts. Researchers in this field hypothesized that once bacteria infiltrate a host cell, the relationship oscillates between infection and harmony. If bacteria multiply too quickly, they risk depleting the host’s resources and triggering an immune response, leading to death of the guest, the host, or both. If it reproduces too slowly, it will not be able to establish itself in the cell. They believed that bacteria achieve a moderate rate of reproduction only in rare cases. Then, to become a true endosymbiont, it must infiltrate its host’s reproductive cycle to reach the next generation. And finally the host Genome They must eventually mutate to accommodate the bacteria, allowing the two to develop as a single unit.

“They became addicted to each other,” Furholt said.